The invention relates to antimicrobial-containing resin compositions, and more particularly synthetic resin compositions incorporating an aromatic derivative of a mono-halogenated phenolic antimicrobial compound, which subsequent to processing, exhibits a level of long-term persistent antimicrobial activity.
In recent years considerable effort has been expended in attempting to develop biostatic-biocidal synthetic resin compositions wherein the antimicrobial activity of the composition is not significantly effected by temperatures and pressures normally encountered in the processing of the compositions into a myriad of final products.
As those well versed in the art of antimicrobial compounds are aware, it is well recognized that the biostatic-biocidal activity of closely related compounds generally varies considerably. The variance in activity is generally not only unpredictable with respect to the compounds per se, but is greatly magnified when such compounds are incorporated in synthetic resin compositions that require the addition of plasticizers, stabilizers, lubricants and pigments in order to render the resin suitable for processing into final products.
Accordingly, the fact that a given compound has per se recognized antimicrobial activity does not in fact assure that such compound will have the same degree of, or any, antimicrobacterial activity when incorporated in other than an inert solvent-carrier. The class of biostats-biocides comprising halogenated phenols is a prime example. While the greater germicidal activity of monohalogen substituted alkyl derivatives of phenol over phenol was recognized in the early 1900's it was almost thirty years before some potent germicidal compounds were discovered among the aromatic derivatives of p-chlorophenol. Among these compounds was the benzyl derivative which was tested against test organisms of the typhoid-colon group. The results proved promising and eventually led to the commercial development of o-benzyl-p-chlorophenol, a potent broad spectrum antimicrobial which in non-aqueous solution has for many years been utilized for the sanitizing of hard surfaces, laundering fabrics, and with dispersing agents, compounded into aqueous detergent compositions having high phenol coefficients.
Therefore, a substantial amount of experimentation is more often than not involved in the development of biostatic-biocidal resin compositions that after processing into a final product retain an effective level of antimicrobial activity over a period of time whereby such products retain such activity during substantially the useful life of the product. It will thus be appreciated that the mere fact that a compound, per se, or in certain solvents or compositions, has antimicrobial properties does not render such compound as an obvious antimicrobial additive for incorporation in synthetic resin compositions, particularly such compositions that must be subjected to relatively high processing temperatures and pressures in order to produce a final consumer product.
Prior art attempts to provide antimicrobial synthetic resinous compositions, as distinguished from merely precluding microbial degredation of polymeric compositions, have often utilized organo-metallic compounds, particularly those based on mercury, tin, arsenic, copper as the active antimicrobial compound. Other classes of antimicrobial compounds include brominated salicylanilides, mercaptans, quaternary ammonium compounds and carbamates, for example. Generally, the above mentioned compounds are characterized by serious drawbacks in that they are highly specific in their antimicrobial activity, highly toxic, thermally degredated, etc., whereby commercial utilization of such compounds is not practical or advisable.
While it is appreciated that many polymers inherently resist biological attack these polymers are seldom used without modification. Other materials such as plasticizers, stabilizers, lubricants, and fillers, necessary to providing resinous compositions that can be molded and extruded on a commercial scale, increases the polymer's vulnerability to fungi and bacteria since they act as a source of food for microorganisms.
Not the least of the problems associated with the molding and extruding of an antimicrobial thermoplastic composition is the provision of a composition capable of withstanding molding and extruding temperatures in the order of 400.degree. to 500.degree. F. Temperatures of this order are necessary for the dispersion of the antimicrobial compound in a thermoplastic synthetic resin, pelletizing of the antimicrobial resinous composition to facilitate handling for subsequent fusion of the pelletized resinous composition to mold or extrude articles and/or film from high molecular weight high density polyethylene, polystyrene, polypropylene, and film grade polyvinylchloride without significant degredation of the active antimicrobial compound incorporated therein.